Mammographic calcifications and risk of subsequent breast cancer.

Background: Women with proliferative benign breast lesions are at increased risk of breast cancer, and some studies have provided evidence that microscopic calcifications in such lesions enhance the risk.

Purpose: This study was performed to determine whether calcifications on mammograms are predictive of subsequent breast cancer.

Methods: Data for this study were collected on women enrolled at four of the clinics that participated in the Breast Cancer Detection and Demonstration Project (BCDDP).

Prospective epidemiological studies involving paired organs.

Standard methods for analysing survival data or case-control data normally concern factors affecting a subject as a whole. However, in a study of a condition that might develop in one or both of a pair of bodily organs information on response and on covariates may be available for each separately. This information can be used to investigate whether the presence of a factor on one side is associated with the condition on that same side, and thus leads to more direct evidence concerning aetiology.